As described in a commentary on pages 192-194 of the Journal of the American Veterinary Medicine Association (JAVMA), Vol. 197, No. 2 (Jul. 15, 1990), the population growth of unwanted pets represents a significant problem in the United States.
The problem of pet overpopulation in the United States reflects a similar problem with feral dogs and cats in developing and third world nations.
As the JAVMA article describes, there are surgical methods for sterilizing dogs, cats, and other pets, but these methods are too expensive to be widely used at effective levels and have associated risks (e.g., anesthesia, infection and hemorrhage). Various products for non-surgical sterilization are currently under investigation, as indicated in the Jul. 15, 1990 article, but none have proven to be entirely satisfactory.
Also, Stagg et al. U.S. Pat. No. 4,356,189 discloses the sterilization of male animals by injection of a weak acid such as lactic acid, or a weak base, into the spermatic cords. A product based on this invention was licensed for cattle by the Food and Drug Administration/Center for Veterinary Medicine, and was being evaluated for dogs, but the license was withdrawn in August of 1990 due to evidence of non-efficacy as a result of variability in administration of the drug. Additionally, this drug was not efficacious in dogs.
Another product under development, zinc tannate, has shown promise in laboratory tests with rodents and rabbits. However, this product has yet to be tested in species intended for treatment, namely, dogs and cats. This agent is not intended for use in food production animals. See U.S. Pat. Nos. 4,156,427 and 4,339,438.
Methods used for oastration of livestock present different types of problems. The procedures are performed by non-veterinarians, and are traumatic on the animals, causing a high incidence of infection, poor growth, hemorrhage and death.
For example, about two percent of the hogs which are castrated every year develop severe disease or die from castration-associated infection. Others are sickened for a period of weeks, which causes their growth to temporarily slow. The actual number of hogs that become sick or die yearly in the United States from castration-associated infection is believed to be on the order of two million. Also, because of abscesses caused by these infections, a large portion of the carcasses or parts of carcasses cannot be used for meat.
Accordingly, there is a major need in both the field of food animal production, and in the field of pets, for an effective way to castrate animals in a manner that is safe and non-injurious to the animal, while being inexpensive as well.
In accordance with this invention an enzymic preparation is used for castration, providing reliable, effective results at low cost, and with little or no pain to the animal. Furthermore, the properly used enzyme system of this invention appear to be safe to the animal so that, for example, millions of hogs can be saved over a period of a very few years by simply using the invention of this application rather than conventional castration. It is expected that similar savings will be found in other kinds of farm animals.
Also, the use of this invention is so simple that it can be used on pets in a widespread manner for the reliable control of pet populations.